I can't assign my villagers to a bed!

I've watched multiple YouTube videos and non of them ever work. Basically, my village is a giant castle and the ground is foundation, but when I try to place a bed in a new area, it only allows me to assign myself to that bed....however, if I place a bed where the old bed was or around that old area...it works. Anybody got the same problem or have the solution? (I attached a picture of my village so maybe someone can see the problem)

I've watched multiple YouTube videos and non of them ever work. Basically, my village is a giant castle and the ground is foundation, but when I try to place a bed in a new area, it only allows me to assign myself to that bed....however, if I place a bed where the old bed was or around that old area...it works. Anybody got the same problem or have the solution? (I attached a picture of my village so maybe someone can see the problem)